Getter ion pump apparatus



Oct 15, 1953 R. zAPHlRoPoULos GETTER ION PUMP APPARATUS Filed Feb. 2, 1961 :t IIL INVENTOR. RENN ZAPHIROPOULOS United States Patent f 3,107,045 GE'ITER ION PUlVIP APPARATUS Renn Zaphropoulos, Los Altos, Calif., assgnor to Varian Associates, Palo Alto, Calif., a corporation of Callfornia Filed Feb. 2, 1961, Ser. No. 86,695 2 Claims. (Cl. 230-69) The present invention relates in general to getter ion vacuum pump apparatus and more specifically to a novel getter ion vacuum pump configuration.

A need has developed in the high vacuum field for -an eficient, small and lightweight getter ion vacuum pump which would be useful in applications such as appendage pumping for electron tubes, vacuum tube production, environmental test equipment, and etc. Certain problems have been encountered in attempts to `develop such a getter ion vacuum pump. Prior pump coniigurations possessed dead spaces in the interior of .the pump which tended to trap contaminating gases and made cleaning operations extremely ditlicult. Difliculty was :also encountered in providing a pump in which gas |leakage into the pump was virtually eliminated and the most eicient use of magnetic flux lines was obtained.

l-t is, therefore, the object of the present invention to provide a Inovel getter ion vacuum pump which is extremely compact and easy to manufacture, lends itself readily to :cleaning operations, substantially eliminates gas leakage, and obtains maximum magnetic field efciency.

One feature of the present invention is a unique cylindrical envelope which results in an unusually compact symmetrical pump structure and 4also facilitates construction thereof.

Another feature of the present invention is the use of concave re-entrant pole faces on an annular permanent magnet yoke which completely surrounds the pump envelope providing support therefore while minimizing the magnetic ux leakage.

Still another feature of the present invention is a novel cathode member which reduces the possibility of dead space within the pump structure.

Still another feature of the present invention is the provision of a unitary structure serving as both the pumps cathode and outer envelope.

Other and 4further features of the present invention will become apparent upon perusal of the following specification taken in connection with the -accompanying drawing, wherein:

FIG. l is a plan view partially cut away showing one embodiment of the present invention,

FIG. 2 is an end view of the pump shown in FIG. l,

FIG. 3 is a perspective view lshowing the novel cathode of the pump shown in FIG. 1,

FIG. 4 is a top view partially cut .away showing another embodiment of the present invention, and

FIG. 5 is a top View partially cut away showing still another embodiment Vof the present invention.

Referring now to the drawings of FIGS. l through 3 there is shown a novel getter ion vacuum pump apparatus of the present invention.

More specifically a hollow, metal, cylindrical envelope 11 having smooth inner and outer side walls is closed off by end walls 12 and 13 suitably sealed to the side walls of envelope 11 to provide a cylindrical vacuum chamber 14. The smooth inner wa-ll of the cylindrical chamber 14 has no dead spaces for the collection of contaminating gases and the smooth outer wall provides a compact st-ructure requiring a minimum of space. The small number of parts comprising the cylindrical chamber 14 requires few connections thereby reducing the possibility of gas leaks.

A pair of cylindrical adapter tubes 15 are carried from ice .two oppositely disposed apertures in the side wall of the envelope 11 and communicate with the cylindrical cham- Iber 14. 'Ihe adapter tubes 15 provide two conductance paths from .the `chamber 14 which may be used in applications requiring the evacuation of two separate chambers with a single vacuum pump.

The cellular anode 16 is supported within cylindrical chamber 14 by the rigid lead-in 17 which extends through an aperture in the end wall 13. High voltage is supplied to the cellular anode 16 via the lead-in 17 which is insulated from the cylindrical envelope 11 by a ceramic insulator 18.

The hollow cylindrical cathode 19 made of reactive material and having substantially .the same outer dimensions as the inner dimensions of the cylindrical casing 11 is .positioned within the chamber 14 and encloses the cellular anode 16. As more clearly shown in FIG. 3 the cylindrical cathode 19 is provided with oppositely disposed apertures 20 and with a longitudinal slit 21 which extends the entire length of the cathode 19. The cathode apertures 20 are positioned so as to communicate with lthe adapter tubes 15 while the slit 21 allows the cylindrical cathode 19 to be spring loaded -against the inner surface of Ithe cylindrical envelope 11. The spring loaded cathode minimizes the possibility of dead space between the cathode and outer envelope 11. The cathode 19 is secured within the chamber 14 by welding to the cylindrical envelope 11 a small tab which extends through a notch 22 at one end of the cathode 19. This maintains the cathode apertures 20 in alignment with the adaptor tubes 15.

The annular permanent magnet yoke 23 is provided with a pair of concave re-entrant poles 24 having substantial-ly the same radius of curvature as does the cylindrical envelope 11 thereby providing a suitable support therefor. The poles 24 are positioned with respect to the cylindrical envelope 11 such that the-magnetic field of the magnet 23 threads through the individual cellular elements of the Ianode 16 in substantial parallelism to the longitudinal axes thereof. The magnet yoke 23 is longitudi- -nally divided into two separate parts each of which has a Itransverse cylindrical opening 25 therein which communicate with the adaptor tubes 15 upon placement of the two separate parts of magnetic yoke 23 to the exterior of cylindrical envelope 11. The annular configuration of the magnetic yoke 23 completely encircles the envelope 11 thereby providing `a very compact symmetrical pump structure which is easy to manufacture, can be used in applications having rigid space limit-ations, and exhibits very little magnetic flux leakage.

In operation a positive potential is applied to the anode with respect to the cathode while a magnetic iield is applied by the permanent magnet. The resulting ionization and bombardment of the negative cathode by positive ions is well known in the getter ion vacuum pump field and will only be described briefly as follows:

Electrons tending to flow to the anode due to the electric field formed lbetween the anode and cathode are -forced into a spiral path by the presence of a strong magnetic field. The greatly increased electron path length results in a high probability of collision between these electrons and gas molecules. These collisions produce gas ions yand more free electrons which in turn collide with other gas molecules, freeing ions and electrons. The positively charged gas ions then bombard the reactive cathode from which atoms are sputtered. The sputtered atoms are deposited on the anode Iand other tube elements forming chemically stable compounds with `the active gas atoms such -as oxygen and nitrogen. The chemically inert gases :are also removed by ion burial in the cathode and by entrapment on the anode.

Referring now to FIG. 4 there is shown another emarezzo/i bodiment which is substantially the same as the apparatus shown in FIGS. l and 2 with the exception of the novel pump envelope and permanent magnet configuration. In panticular, the cup-shaped pump envelope 31 having smooth inner and outer side walls is made of a ceramic material and has its closed end Wall molded around the rigid lead-in 17. This construction eliminates the -need for additional insulators between the lead-in 17 and lthe cathode 19. This embodiment is also modilied for use in applications requiring evacuation of only a single chamber by replacing the oppositely disposed apertures in the side walls of the `envelope 11 shown in FIG. 1 with an open end 32 which communicates with and is brazed Ito a single adaptor tube 33. This pump coniiguration makes the two part construction and the transverse `cylindrical openings of the magnets shown in FIGS. l and 2 unnecessary. The single piece Iannular magnetic yoke member 34 of this embodiment may be slid over the end of the pump for mounting on the cylindrical ceramic envelope 31.

The operation of this embodiment is essentially the same as that described for the apparatus shown in FIGS. 1

The embodiment of FIG. 5 operates in essentially the same manner as that `described for t-he apparatusishown in FIGS. l and 2.

The above embodiments thus clearly illustrate novel improved getter ion pump apparatus which is extremely compact and efhcient and which requires a minimum of production techniques.

Since many changes could be made in the abovev construction -and many apparently widely different yembodiments of this invention could be made Without departing trom the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a -limiting sense.

What is claimed is:

l. An electrical vacuum pump apparatus including, an anode member subdivided into a plurality of cellular compartments, a reactive cathode member disposed opposite the open end of Vsaid cellular compartments and being spaced therefrom, a hollow essentially smc-oth walled cylindrical envelope member enclosing `said anodeand ycathode members, said cathode member being a hollow essentially smooth Walled envelope conforming to the wal-ls of `said cylindrical envelope member, and being provided with a longitudinal slit allowing it to be springloaded within said cylindrical envelope member.

2. An electrical vacuum pump apparatus including, an anode member, a cathode member, a hollow envelope enclosing said anode `and Icathode members, a magnetic yoke having a plurality of -re-entrant pole yfaces for producing and directing a magnetic eld between said anode and cathode members, said magnetic yoke completely en-V circling said hollow envelope, `said re-entrant lpole faces conforming to the outer Wall of said hollow envelope, and said hollow envelope lhaving essentially smooth cylindrical walls, said cathode member comprising -a hollow essentially smooth Walled ycylinder conforming sto Ithe walls of said cylindrical envelope and "being provided with a longitudinal slit allowing it to be spring-loaded within said cylindrical envelope.

References Cited in the file of this patent UNITED STATES PATENTS 2,941,099 Picard et a1. c June 14, 1960' FOREIGN PATENTS 1,207,893 France sept. 7, 1959 

1. AN ELECTRICAL VACUUM PUMP APPARATUS INCLUDING, AN ANODE MEMBER SUBDIVIDED INTO A PLURALITY OF CELLULAR COMPARTMENTS, A REACTIVE CATHODE MEMBER DISPOSED OPPOSITE THE OPEN END OF SAID CELLULAR COMPARTMENTS AND BEING SPACED THEREFROM, A HOLLOW ESSENTIALLY SMOOTH WALLED CYLINDRICAL ENVELOPE MEMBER ENCLOSING SAID ANODE AND CATHODE MEMBERS, SAID CATHODE MEMBER BEING A HOLLOW ESSENTIALLY SMOOTH WALLED ENVELOPE CONFORMING TO THE WALLS OF SAID CYLINDRICAL ENVELOPE MEMBER, AND BEING PRO- 